Medical Utilization Associated with Palivizumab Compliance in a Commercial and Managed Medicaid Health Plan

BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections and hospitalization in infants. Palivizumab is currently the only available agent for prevention of RSV infection in highrisk infants. This high-cost injectable requires monthly dosing during the RSV season. Compliance with the injection schedule is important in the prevention of RSV infection and respiratory complications. Managed care organizations have an interest in the relationship between compliance with the palivizumab dosing schedule and respiratory-related medical outcomes such as emergency room (ER) visits, physician office visits, and hospitalizations. OBJECTIVES: To evaluate respiratory-related medical outcomes and cost for infants who were prescribed and received palivizumab in accordance with the dosing schedule recommended by the American Academy of Pediatrics (AAP) in 2006 versus those who did not. METHODS: A retrospective claims analysis was conducted to assess the relationship between compliance with the palivizumab dosing schedule and respiratory-related medical visits and costs in a western Pennsylvania managed care organization composed of approximately 307,000 commercial and 92,000 Medicaid members. De-identified pharmacy and medical claims data were extracted for infants (0-24 months) who met prior authorization criteria and who received at least 1 dose of palivizumab during the 2006-2007 RSV season (October 15, 2006, to April 15, 2007). Patient compliance was based on (a) starting palivizumab on time, (b) receiving the expected number of injections, and (c) no more than a 37-day gap between palivizumab claims. Medical utilization (physician office visits, ER visits, and hospital admissions) was analyzed by comparing medical services (with respiratory-related ICD-9-CM codes) for the compliant versus noncompliant groups. Net health plan costs (after subtraction of member cost share) were compared for compliant versus noncompliant groups for (a) palivizumab-only pharmacy cost; (b) the cost of RSV-related medical services; and (c) the cost of all respiratory-related medical services, excluding those provided during the inpatient newborn stay. The associations between compliance and other patient variables were assessed using the Mann-Whitney U test for nonparametric data and Pearson chi-square or Fisher's Exact tests for categorical data. RESULTS: Of the 245 infants who received palivizumab during the 2006-2007 RSV season, 151 (61.6%) were first-season recipients of palivizumab, and 131 (53.5%) were male; 145 (59.2%) belonged to a Medicaid benefit plan, and 100 (40.8%) belonged to a commercial benefit plan; and 73 (29.8%) were deemed to be compliant with the 2006 AAP recommended palivizumab dosing schedule. Fourteen (19.2%) of compliant infants had at least 1 respiratory-related hospital admission compared with 37 (21.5%) of noncompliant infants (P = 0.734). The proportions of infants with at least 1 respiratory-related physician office visit were also similar for the 2 groups, 60.3% (n = 44) for compliant infants versus 64.5% (n = 111) for noncompliant infants (P = 0.564). There was a significant difference in the proportion of infants with at least 1 respiratory-related ER visit, 15.1% (n = 11) of compliant infants versus 28.5% (n = 49) of noncompliant infants (P = 0.034), but there were no RSV-related ER visits in either group and no significant differences between the groups in the proportion with at least 1 RSV-related office visit (9.6% for compliant infants vs. 5.8% for noncompliant infants, P = 0.284). RSV-related hospitalization occurred in 0 (0.0%) compliant and 2 (1.2%) noncompliant infants (P = 1.000). Compliant infants had significantly higher median per patient palivizumab pharmacy costs ($10,416) compared with noncompliant infants ($7,605, P = 0.011). However, median total (palivizumab and respiratory-related medical) costs for the 2 Groups did not significantly differ (P = 0.189). CONCLUSIONS: About 30% of the infants who received palivizumab during the 2006-2007 RSV season were compliant with dosing recommendations. Compliance was associated with a lower proportion of infants with at least 1 respiratory-related ER visit but not with any other study outcome, including the proportion of infants with at least 1 hospital admission or physician visit or any measure of RSV-related use. Median palivizumab per patient costs were higher for the compliant group, but there was no significant between-group difference in total median per patient cost (palivizumab drug plus respiratory-related medical cost).

RESULTS: Of the 245 infants who received palivizumab during the 2006-2007 RSV season, 151 (61.6%) were first-season recipients of palivizumab, and 131 (53.5%) were male; 145 (59.2%) belonged to a Medicaid benefit plan, and 100 (40.8%) belonged to a commercial benefit plan; and 73 (29.8%) were deemed to be compliant with the 2006 AAP recommended palivizumab dosing schedule. Fourteen (19.2%) of compliant infants had at least 1 respiratory-related hospital admission compared with 37 (21.5%) of noncompliant infants (P = 0.734). The proportions of infants with at least 1 respiratory-related physician office visit were also similar for the 2 groups, • Respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract infections, and each year accounts for approximately 75,000 to 125,000 hospitalizations in infants younger than 1 year of age. Palivizumab is currently the only available FDA-approved agent to prevent RSV infection in neonates but is very costly and requires monthly injections during the RSV season. • Children at highest risk of complications from RSV infection include premature infants, children less than 2 years of age with congenital heart or chronic lung disease, and children with immune systems that are compromised by a medical condition or medical treatment. • Because of the frequent dosing schedule for palivizumab, noncompliance is common and may be the most controllable barrier to pharmacologic prevention of RSV infection and its potentially severe sequelae in high-risk infants. Several previous studies have yielded mixed results regarding the relationship between palivizumab compliance and improved infant respiratory health.

R E S E A R C H
60.3% (n = 44) for compliant infants versus 64.5% (n = 111) for noncompliant infants (P = 0.564). There was a significant difference in the proportion of infants with at least 1 respiratory-related ER visit, 15.1% (n = 11) of compliant infants versus 28.5% (n = 49) of noncompliant infants (P = 0.034), but there were no RSV-related ER visits in either group and no significant differences between the groups in the proportion with at least 1 RSV-related office visit (9.6% for compliant infants vs. 5.8% for noncompliant infants, P = 0.284). RSV-related hospitalization occurred in 0 (0.0%) compliant and 2 (1.2%) noncompliant infants (P = 1.000). Compliant infants had significantly higher median per patient palivizumab pharmacy costs ($10,416) compared with noncompliant infants ($7,605, P = 0.011). However, median total (palivizumab and respiratory-related medical) costs for the 2 groups did not significantly differ (P = 0.189).
R espiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections and the leading cause of hospitalization in infants, accounting for approximately 75,000 to 125,000 pediatric hospitalizations in children less than 1 year of age in the United States each year. [1][2][3][4][5][6][7] It is estimated that approximately two-thirds of all infants are infected with RSV within their first year of life and nearly all are infected by 2 years of age. 2,3 RSV infections typically occur from November through March in most communities throughout the United States. 8 Similar to the common cold, there is no standard treatment protocol for RSV infection and the virus will typically run its course in 8 to 15 days. Risk factors such as premature birth or chronic lung or heart conditions increase the chance for more severe and potentially life-threatening RSV infection. 8 Palivizumab (Synagis), a humanized monoclonal antibody, is approved by the U.S. Food and Drug Administration (FDA) for the prevention of serious respiratory tract disease caused by RSV in pediatric patients at high risk of RSV disease. 9 The recommended dose is 15 milligrams per kilogram intramuscularly every 28-30 days, beginning prior to the start of RSV season, to maintain adequate antibody trough levels during the season. 9 In the initial IMpact-RSV randomized controlled trial (1996-1997 RSV season), palivizumab was shown to reduce RSV hospitalizations by 55% in high-risk patients compliant with the monthly dosing schedule. 10 However, patient compliance with the dosing schedule is not optimal, as documented in the Palivizumab Outcomes Registry Study, which found only 59.3% compliance based on appropriate number of doses and timing. 11 Potential factors associated with poor compliance with the dosing schedule include Medicaid insurance coverage, family tobacco smoking, and parental perception of drug efficacy. [12][13][14][15] Managed care efforts to improve compliance with the palivi-Medical Utilization Associated with Palivizumab Compliance in a Commercial and Managed Medicaid Health Plan zumab dosing schedule could potentially offset the increased palivizumab costs by decreasing emergency room (ER) visits, physician office visits, and hospitalizations. One such effort, tested by Gentiva Health Services, involved a national in-home RSV prophylaxis program, which was associated with high compliance and potential cost savings. 16 Analysis of data in the Palivizumab Outcomes Registry reported by Frogel et al. (2008) produced a contrary finding of no significant association between compliance and RSV hospitalizations when compliance was defined as the number of expected injections. 11 Joffe et al. (1999) found that the cost-effectiveness of palivizumab varied widely depending on the infant's baseline level of risk and "in general the cost of prophylaxis against RSV infection appeared high, relative to the benefits realized." 17 Given the conflicting results of previous studies of palivizumab compliance and cost-effectiveness, the purpose of this study was to further evaluate the relationship of palivizumab compliance with respiratory-related utilization and costs.

■■ Methods Design
A retrospective analysis of an administrative claims database was conducted to determine the impact of noncompliance with the 2006 American Academy of Pediatrics (AAP) recommended palivizumab dosing schedule on respiratory-related medical services and costs from the perspective of a western Pennsylvania managed care organization (MCO) covering approximately 500,000 members (307,000 commercial plan members, 92,000 Medicaid plan members, and 108,000 Medicare plan members) during the study period. For the purpose of this analysis, data were evaluated from the commercial and Medicaid groups only. This analysis was approved as a quality improvement (QI) study under the auspices of the QI review subcommittee of the MCO.

Inclusion/Exclusion Criteria
De-identified pharmacy and medical claims data were extracted for infants meeting the following inclusion criteria: (a) continuous enrollment during the 2006-2007 RSV season ( October 15, 2006, to April 15, 2007); (b) 0-24 months of age as of the start of the RSV season; (c) pharmacy claims approved via the plan's prior authorization process for palivizumab (Table 1); and (d) at least 1 paid claim for palivizumab during the 2006-2007 RSV season. Compliance was defined as meeting all 3 of the following criteria: (a) starting palivizumab on time; (b) refilling palivizumab on time; and (c) receiving no more than 6 injections per RSV season, pursuant to the health plan's quantity limit which was less restrictive than the 2006 AAP guidelines that advised, "changes from this recommendation of 5 monthly doses require careful consideration of the benefits and costs." 8

What this study adds
from the study, since they are not high enough to have included the cost of the drug, and it was assumed these were miscoded claims or claims for drug administration fees. Medical services were captured from the MCO's medical claims data warehouse and included all claims with a respiratory diagnosis coded in any field on the claim based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes (Table 2). Diagnosis codes selected were reviewed with physicians to ensure relevance. Visits were classified as ER, hospital, or physician office using 2 methods. First, some claims were classified using CPT codes for evaluation and management services. For office visits, these codes included 99201-99205 for new patients; 99211-99215 for established patients; 99241-99245 for consultations; 99381, 99382, 99391, and 99392 for preventive care; and 99431, 99432, 99433, and 99435 for newborn care. For inpatient services, a partial list of evaluation and management codes was used, including 99221-99223 for initial hospital admission visit; 99231-99233 for subsequent hospital visit; 99293-99296 for pediatric critical care and neonatal intensive care unit care; 99251-99255 for consultation; and 99217-99220 for observation. For ER visits, codes 99281-99285, indicating emergency department evaluation and management, were used. Second, for claims on which a CPT code was not billed, revenue codes were used to identify claim type. Inpatient hospital admissions were identified by room and board revenue codes 100-179 plus place of service code 21. ER visits were identified by revenue codes 450-459 plus place of service code 23. Respiratory-related services provided during the initial newborn hospital stay were excluded from respiratory-related medical service utilization and cost.
prior to the season were required to have a first pharmacy claim for palivizumab on or before November 30, 2006, and subsequent claims had to occur within 37 days of the previous claim. Members born during the RSV season were assumed to receive their first dose as an inpatient and were required to have their first outpatient palivizumab pharmacy claim within 37 days of hospital discharge. Each subsequent claim had to occur within 37 days of the previous claim.
Patient compliance with the individualized palivizumab administration schedule was evaluated by comparing the number of injections identified in pharmacy claims with the expected number of injections based on date of birth and the recommended monthly dosing frequency. Infants who received an injection on or after March 15, 2007, were not required to receive an injection in April to be considered compliant, since their titer levels should have been sustainable up to 30 days post-injection, thereby carrying them through the remainder of the RSV season ending April 15, 2007. A 37-day allowable gap between claims was chosen as the measure of compliance to allow the patient time to receive the drug from the specialty pharmacy provider and make a physician office visit for administration.
Palivizumab claims were identified via pharmacy claims; Current Procedural Terminology (CPT) code 90378; and Healthcare Common Procedure Coding System (HCPCS) codes C9003, J1565, and S9562. Of note, this particular MCO has code C9003 blocked at place of service number 11 (physician office) and also uses physician mailings to encourage parents to fill prescriptions for palivizumab through the MCO's specialty pharmacy provider. Therefore, nearly all palivizumab claims in this study were under the pharmacy benefit. Medical claims for palivizumab with a dollar amount less than $500 were excluded  8 Only pharmacy claims were subject to prior authorization. CHD = hemodynamically significant congenital heart disease including congestive heart failure, severe pulmonary hypertension, or cyanotic heart disease; CLD = chronic lung disease requiring medical therapy such as supplemental oxygen, bronchodilator, diuretic, or corticosteroid therapy within 6 months before the start of RSV season; RSV = respiratory syncytial virus.

Analysis
Infants were first categorized as compliant (i.e., filled prescriptions for palivizumab in accordance with the dosing schedule recommended by the 2006 AAP guidelines) or noncompliant. Baseline characteristics were then compared for compliant and noncompliant infants, including first versus second season exposure to palivizumab, gender, type of insurance coverage, and duration of follow-up. Length of follow-up was analyzed using patient months, which were calculated as the actual number of coverage months for each infant from the beginning of the season or birth to the end of the season. A maximum of 7 patient months were counted for infants born prior to the start of the RSV season. This comparison was done to account for varying lengths of follow-up due to birth date. For example, an infant born in November would have 5 months of follow-up, whereas an infant born in February would only have 2 months of follow-up. This variation in length of follow-up could account for differences in the amount of medical claims incurred.
The primary outcomes were the proportions of patients with at least 1 respiratory-related ER visit, hospital admission, and physician visit. Furthermore, medical services were more specifically assessed to determine the percent of patients with at least 1 RSV-related ER visit, hospital admission, and physician office visit. RSV-related visits were defined as those with an ICD-9-CM code of 079.6 (RSV infection), 466.11 (acute bronchiolitis caused by RSV), or 480.1 (pneumonia caused by RSV).
A descriptive analysis of cost outcomes was performed to compare health plan paid costs for compliant and noncompliant infants. Health plan paid costs (i.e., after subtraction of patient cost share) were assessed for palivizumab pharmacy costs and respiratory-related medical services during the entire RSV season from October 15, 2006, to April 15, 2007. Costs were reported as the mean and median per patient cost for the season for total respiratory-related medical services and RSV-related medical services (codes in Table 2). Additionally, mean per patient per month (PPPM) costs were calculated for total cost (palivizumab pharmacy and total respiratory-related medical).
Patient characteristics for compliant versus noncompliant infants, including first-season versus second-season exposure to palivizumab, gender, and type of insurance coverage, were analyzed using the Pearson chi-square test. The between-group difference in duration of follow-up in patient months was analyzed using the Mann-Whitney U test. Respiratory-related medical visit comparisons and cost comparisons were analyzed using the Mann-Whitney U test for nonparametric data and Fisher's Exact test for categorical data. All statistical analyses were performed using SPSS version 17.0 (SPSS Inc., Chicago, IL). The a priori P value for statistical significance was 0.05.

■■ Results
From October 15, 2006, to April 15, 2007, a total of 245 infants met the inclusion criteria, including receipt of at least 1 dose of palivizumab ( Figure 1). There were 10 infants with palivizumab claims that were medical rather than pharmacy claims, and 5 of

Diagnoses and Codes Used to Define Respiratory-Related and RSV-Related Services
medical event, there were no significant differences between the compliant versus noncompliant groups in RSV-related hospitalizations (0.0% vs. 1.2%, respectively, P = 1.000) or physician office visits (9.6% vs. 5.8%, respectively, P = 0.284), and there were no RSV-related ER visits in either group.
Cost analyses showed that although the median per patient palivizumab cost was significantly higher in the compliant group ($10,416 vs. $7,605, P = 0.011), the median total per patient costs (palivizumab-related pharmacy and respiratory-related medical services) for the 2 groups were not significantly different ($12,466 vs. $10,600, P = 0.189).

■■ Discussion
During the 2006-2007 RSV season, only 29.8% of patients were compliant with receiving doses of palivizumab as recommended by the 2006 AAP guidelines. 8 Compared with noncompliance, compliance with palivizumab therapy was associated with a significantly lower proportion of patients with at least 1 respiratory-these infants had medical claims only, which meant that these 5 infants were not subject to prior authorization for coverage of palivizumab. Of the 245 infants included in the study, 73 (29.8%) were determined to be compliant with palivizumab injections, and 172 (70.2%) were noncompliant (Table 3).
A higher proportion of compliant patients (71.2%) were first-season recipients of palivizumab compared with 57.6% of noncompliant patients (P = 0.044; Table 3). Although the median duration of patient follow-up was 7 months in both groups, the Mann-Whitney U test result was statistically significant (P = 0.039) because of differences in the distribution of values.
Analysis of the number and percent of patients with at least 1 respiratory-related ER, hospital, or physician visit showed that the noncompliant group had a higher rate of patients with at least 1 respiratory-related ER visit (28.5% [n = 49]) compared with compliant patients (15.1% [n = 11], P = 0.034) but no significant differences in hospital admissions (P = 0.734) or physician visits (P = 0.564; Table 4). For the measure of at least 1 RSV-related

Medical Utilization Associated with Palivizumab Compliance in a Commercial and Managed Medicaid Health Plan
Yes (n = 73) No (n = 67)

Flowchart for Patient Selection
Continuously enrolled members during study period a (N = 386,873) a Study period was October 15, 2006, through April 15, 2007 Refers to whether each claim occurred within 37 days of the previous claim. hospitalization, prior use of palivizumab, mechanical ventilation, active or recent RSV infection, hepatic or renal impairment, and seizure disorder. Differences between the results of IMpact-RSV and the present study could be partly attributable to the more stringent exclusion criteria used in IMpact-RSV. Additionally, the IMpact-RSV Study is more than a decade old and was sponsored by the manufacturer of palivizumab as 1 of the clinical trials used in the drug approval process. 9,10 Another study, conducted by the Palivizumab Outcomes Registry Study Group (2008), was a prospective, observational registry that collected data on infant palivizumab prophylaxis and outcomes for 19,548 enrollees from 2000 to 2004. That study found a 59.3% compliance rate with palivizumab based upon infants receiving the appropriate number of doses on time (within 35 days of the previous injection). There was no association found between compliance, defined as receiving appropriate number of doses, and RSV hospitalizations. However, compliance, when defined as receiving all doses on time, was associated with a significantly lower odds of RSV hospitalization. 11 Potential reasons for differences in results compared with the present study include the larger patient sample size, the prospective design, and the way in which compliance was defined. The Palivizumab Outcomes Registry Study Group gathered specific information on exact date and dose of each injection, whereas the present study assumed injection date as the date of the paid palivizumab claim, which could have resulted in an inaccurate determination of compliance. Additionally, the Palivizumab Outcomes Registry Study Group considered compliance as receiving the expected total number of injections for the season based on the month the first injection was given with no more than a 35-day gap. The present study considered 3 factors in defining compliance: receipt of the first dose after hospital discharge on time, the appropriate related ER visit but similar proportions of patients with at least 1 hospitalization or physician visit with a respiratory-related diagnosis. Although there were no statistically significant differences between the 2 groups for the measures of RSV-specific medical events and there were no RSV-related ER visits in either group, it is of note that 9.6% of compliant patients had an RSV-related physician office visit. Compliance with palivizumab was not significantly associated with overall costs per patient during the study period-that is, the median combined palivizumab plus respiratory-related costs were similar between the groups.
The results of this study seem to imply limited short-term (same RSV season) benefits of palivizumab therapy, since compliant patients continued to utilize respiratory-related medical services and RSV-related office visits. However, the long-term implications of palivizumab use and compliance were not assessed. For example, there is controversy regarding the link between RSV and asthma development later in life. The link between RSV and asthma has been evaluated in several studies, 18 including 1 study of 140 children aged 7 and one-half years with a history of RSV hospitalization during infancy that found 30% of children with a history of RSV had developed asthma compared with 3% of children in the control group (P < 0.001). 19 However, this link remains to be proven and was not considered in the present short-term study for the 2006-2007 RSV season.
Several previously published studies regarding the impact of palivizumab compliance on medical outcomes have shown mixed results. The IMpact-RSV Study (n = 1,502), a randomized controlled trial, found a 93% compliance rate with a monthly dosing schedule of 5 palivizumab injections, resulting in a 55% reduction in RSV hospitalization compared with placebo. 10 However, the IMpact-RSV Study had a long list of exclusion criteria, including hemodynamically significant coronary heart disease, prior was also sponsored by the manufacturer of palivizumab and was initiated in the 2000-2001 RSV season. The present study provides a retrospective review independent of the manufacturer and offers a more current evaluation of a sample of treated infants. Given the results of the present study, as well as the mixed results of the Palivizumab Outcomes Registry Study Group, the cost-effectiveness of palivizumab prophylaxis comes into question. A cost-effectiveness analysis by Joffe et al. (1999) assessed the medical and work-loss costs per hospitalization averted in a hypothetical cohort of premature infants and estimated number of injections, and a gap of no more than 37 days between palivizumab claims. Furthermore, the Palivizumab Outcomes Registry Study Group collected data specific to RSV admission any time a study participant was hospitalized with primary or secondary RSV infection. The present study assessed retrospectively any hospital admission (excluding the initial newborn hospital stay), ER visit, or office visit in which a respiratory diagnosis or a diagnosis of RSV was made but did not have available specific RSV laboratory testing to confirm RSV as the reason for the utilization. Finally, the Palivizumab Outcomes Registry Study Group through medical codes were not subject to prior authorization, since this requirement applies only to the pharmacy benefit. Therefore, we do not know if these patients met the 2006 AAP guideline requirements for palivizumab use. However, palivizumab was billed through medical claims for only 5 infants, 2% of our sample. Finally, the short duration of follow-up would not capture potentially favorable longer-term outcomes associated with healthier infants with fewer chronic respiratory problems.

■■ Conclusions
Palivizumab compliance was suboptimal. Compliance with the palivizumab dosing schedule based on 2006 AAP criteria, compared with noncompliance, was associated with higher palivizumab drug costs but similar overall total costs (palivizumab plus respiratory-related medical costs). Compliance was associated with a lower proportion of patients with at least 1 respiratory-related ER visit but similar proportions of patients with at least 1 respiratory-related physician office visit or hospitalization and similar proportions of patients with any RSV-related service. Ten percent of compliant infants had at least 1 RSV-related office visit during the study period. Further studies are needed to assess the long-term respiratory health and associated medical cost differential between infants who are compliant and noncompliant with palivizumab.
that palivizumab prophylaxis costs anywhere from $12,000 to $420,000 per hospitalization averted, depending upon the risk and gestational age category of the infant. While cost-effectiveness varied widely among different subgroups of infants, the study authors concluded that "in general the cost of prophylaxis against RSV infection appeared high, relative to the benefits realized." The investigators went on to say that this cost-ineffectiveness called for more stringent recommendations for palivizumab. 17 An article in the April 16, 2008, issue of the Wall Street Journal, "Weighing Which Babies Get a Costly Drug," suggested that the few infants who benefit from palivizumab may not justify the high cost of the preventive therapy. 20 Perhaps the key to cost-effective treatment is in utilization management of these drugs. The need for utilization management increases with the anticipated approval by the FDA of motavizumab, another RSV preventive treatment. 21 The present study's MCO has updated its prior authorization criteria to further refine criteria for access to palivizumab treatment based on the 2009 guidelines set forth by the AAP. 22 This 2009 update further restricts access by redefining the gestational age categories and (a) specifically restricts the maximum number of doses to the lesser of 3 doses or coverage up to 90 days of age for the group of patients born at gestational ages from 32 weeks, 0 days through 34 weeks, 6 days and born within 3 months before the start of the RSV season or any time throughout the RSV season; and (b) considers this group eligible only if they have 1 of 2 risk factors (previously several risk factors were considered). Additionally, the 2009 AAP guidelines also make clear that the maximum number of palivizumab injections is 5 per season regardless of the start date in a given geographic region. These recommendations imply that palivizumab was given in an overly broad patient population in prior years and may explain mixed results in assessments of outcomes and cost-effectiveness of palivizumab. Further studies are needed to assess the outcomes in this newly defined and more restricted population for recommended use of palivizumab.

Limitations
First, this was an exploratory and descriptive study of a small sample of infants. The results do not constitute a definitive test of either the effectiveness of palivizumab or the cost-effectiveness of compliance. Second, the method used to categorize compliance was somewhat subjective. This MCO chose to use palivizumab claims data (including pharmacy, medical, and home health administrative claims using appropriate C, J, CPT, and S codes) for determining compliance, permitting 37 days between claims to allow time for the parent to either inject or obtain injection of the drug. A more accurate analysis might have been achieved by querying the data for physician claims for drug administration to augment the fill dates for palivizumab pharmacy claims. However, we believe that the permitted gap of up to 37 days between fill dates of palivizumab at the specialty pharmacy avoided an overestimate of noncompliance.
Third, patients whose palivizumab claims were billed only